Its so-called ‘public option' provider would use the NZ Superannuation Fund's Guardians as its investment manager and have either Inland Revenue or Kiwibank as the administration manager.

Green Party Co-leader Russel Norman says "a significant part of New Zealanders' savings get eaten away by costs and fees."

He says "the current costs and fees faced by KiwiSavers are prohibitively high reducing the incentives to join and eroding the value of KiwiSavers' nest eggs at retirement."

He argues this new option, would "lower costs sizably, saving tens of thousands of dollars," said today.

"If these savings are reinvested, KiwiSavers' nest eggs will be significantly higher, up to $142,000 higher in some cases ($64,000 in today's dollars).

"We will do for superannuation, what Kiwibank has done for banking. We will ensure there is a value for money public option.

He says significant fee and cost reductions would come through greater economies of scale.

"The Super Fund is the only purpose-built superannuation fund that's big enough to secure wholesale cost savings. The Guardians manage a $16 billion fund compared with

the $2.9 billion of assets managed by the six current default providers."

While the Greens talked of a seventh default provider Norman also referred, in his press statement yesterday, to having a single large default provider.

Full details of the policy are not yet available however there is a Q&A document here.